Solid lubricant containing compositions



annals Patented Jan. 1, 19613 3,071,543 SOLlD LUBRICANT CGNTAENENGCDMPOSITISNS Zeil G. McGee, Haverford, Pa, assignor to McGee ChemicalCompany, Inc, Upper Darby, P3,, a corporation of Pennsylvania NoDrawing. Filed July 12, 1960, Ser. No. 42,238 8 Claims. (til. 252-45)This invention relates to lubricating compositions and more specificallyit relates to lubricating compositions containing a solid lubricantsuitable for use at high temperatures under extreme pressure loads. Thisapplication is a continuation-in-part of my copending application SerialNo. 772, 634, filed November 10, 1958, and now abandoned, entitled SolidLubricant Containing Compositions.

The lubrication of the chains in bakery ovens is a typical example of adifficult problem in lubrication since high temperatures, i.e. up to 500F. are regularly encountered with loadings in the extreme pressurerange. Numerous types of lubricants have been developed heretofore tosolve such problems of lubrication but each proved to be inadequate forone or more reasons.

One of the earliest lubricants and one which is still in use comprises asolid lubricant such as graphite dispersed in kerosene. In order toapply this lubricant, however, it is necessary to cool the oven chainsto at least 200 F. and preferably lower because of the low flash pointof the kerosene. Once the lubricant has been applied the kerosene mustbe removed by heating in order to deposit the graphite onto the bearingsurfaces. On numerous occasions when the chains have been heated toorapidly after lubrication, explosions and fires have occurred which haveresulted in severe injuries to personnel. Moreover, the kerosene smokesbadly as it is being removed and it also gives off very obnoxious odors.Since the flavor of bread as well as the flavor of other bakery productsis extremely sensitive to odors, it is necessary to employ lubricatingcompositions which will not give off obnoxious odors when the liquidvehicle is vaporized. Kerosene and similar petroleum hydrocarbonsgenerally contain mercaptans and other sulfur compounds which, althoughthey may be present in very small amounts, have such obnoxious odorsthat when the hydrocarbons containing them are vaporized strong andpenetrating odors are produced. In addition they carbonize some- What onthe metal surfaces, which interferes with smooth lubrication andoperation of the chains.

Polymer oils such as the polyisobutylenes were thought to be suitable asa vehicle for solid lubricants since these were produced syntheticallyfrom compounds free of sulfur and similar odor causing elements andsince they decomposed upon heating into their monomers, i.e. theydepolymerized, so that carbonizing was avoided. Lubricants containingpolyisobutylene as the dispersing agent for the solid lubricant werefound to be unsuitable since at the lower viscosity levels which wouldprovide suflicient lubrication and penetration of the lubricant, thefire and explosion hazard was too great, while if a higher molecularweight polyisobutylene was employed to reduce the fire hazard thelubricant did not penetrate because of its high viscosity and thus thesolid lubricant could not form a film over the bearing surfaces.Subsequently to avoid the fire hazard and provide a sufficiently lowviscosity a third type of lubricant was formulated which consisted of adispersion of the solid lubricant in water. It was found that theevaporation rate was too rapid to permit the lubricant film to penetrateand form over the bearing surfaces and since the metal surfaces were notcovered completely they developed rust and seized.

A composition now has been found which can be applied without coolingthe ovens from their normal operating temperatures of around 400 F. andwhich substantially completely avoids the dangers of fire andexplosions. This lubricant composition provides an improved vehicle fordepositing the solid lubricant onto the hot bearing surfaces. Thisvehicle does not carbonize, its viscosity and evaporation rate arecontrolled to provide maximum contact of the solid lubricant with thebearing surfaces and it prevents rusting and corrosion of adjacent partsof the machinery. Moreover, the vehicle may be vaporized from the hotbearing surfaces without the projection of any objectionable smoke orodors.

Accordingly it is an object of this invention to provide ew and improvedlubricating compositions.

It is another object to provide new and improved extreme pressurelubricants.

It is another object to provide new and improved extreme pressurelubricants capable of high temperature application and use.

It is another object to provide a new and improved lubricatingcomposition which Will deposit a solid lubri cant uniformly over hotbearing surfaces which are sub ject to extreme pressure loads such thatwear and corrosion are minimized.

Additional objects of this invention will be apparent from thedescription and claims that follow.

in accordance with the present invention, and in its broadest aspects, alubricating composition is provided wherein a solid lubricant isdispersed in an emulsion of a specific synthetic oil and water. In itsmore specific aspects, the lubricating composition described may alsocontain certain other components which may or may not be requireddependent upon the specific use of the lubricant but which add to theusefulness of the finished composition as will be described in detail.

The solid lubricants which may be used in the present composition arethose materials which because of their plate-like molecular structureare peculiarly suited for the dry lubrication of metal bearing surfaces.Graphite and molybdenum disulfide are examples of these materials whichare useful for lubricating metal bearing surfaces and are the preferredsolid lubricants for this invention. j

The specific synthetic oils which are emulsified with Water to provide avehicle for the graphite or molybdenum disulfide solid lubricant are thepolyalkylene glycols such as the polyethylene glycols and thepolypropylene glycols. The polyethylene glycols are particularlypreferred. These pre-erred glycols are the oil soluble high molecularweight glycols which range in molecular weight from to about 2000. Aparticularly preferred glycol is a polyethylene glycol having aviscosity of 400- Saybolt Seconds Universal at 000 F., a flash point of490 F. and a fire point of 585 F. A second preferred glycol is apolyethylene glycol having a viscosity of 300 Saybolt Seconds Universalat 100 F. These glycols are the wellknown commercially availablepolyalkylene glycols sold under the trade name of Ucon fluids. The firstof the above-mentioned preferred compounds has the specific designationUcon LB-400X and the second preferred compound, Ucon LB-300-X. Inparticular, those glycols having a viscosity ranging between about '70and 500 Saybolt Seconds Universal at 100 F. are suitable for use in thecomposition of this invention.

It has been found necessary to employ an agent which will assist inemulsifying the above described synthetic oils and water to produce astable emulsion. In addition, it is necessary that such emulsifyingagent when vaporized along with the water and oil from the hot bearingsurface will not decompose to give compounds having obnoxious odors.

Certain polyoxyalkylene compounds have been found to be particularlysuitable as emulsifying agents for the synthetic oil, solid lubricantand water composition of this invention. In addition, thesepolyoxyalkylene compounds because of their surface activity, behave aswetting agents which promote the uniform distribution of the wateremulsion over the metal surfaces and thus promote proper coverage andadherence of the solid lubricant to the metal bearing surfaces. Thespecific polyoxyalkylene compounds which provided the combination ofemulsification characteristics and wetting characteristics are thosecompounds which are sold under the trade name of Pluronics, Thesepreferred compounds are so-called block polymers. They are prepared byadding propylene oxide to the two hydroxyl groups of propylene glycol.The resulting polyoxypropylene chain has hydrophobic properties and canbe made to any controlled length varying in molecular weight from 800 toseveral thousand. Ethylene oxide is added to both ends of thepolyoxypropylene hydrophobic base to give the polyoxyethylenehydrophilic groups on the ends of the molecule. This reaction may becontrolled so that the hydrophilic groups have a controlled length suchthat they constitute from percent to 90 percent by weight of the finalmolecule. The Pluronics particularly preferred for the combinationemulsification and wetting agent of this invention are the liquids inwhich polyoxypropylene hydrophobic base has a molecular weight rangingfrom about 1200 to about 2100 and preferably about 1750 with from 10weight percent to approximately 40 weight percent of the moleculeconsisting of hydrophilic polyoxyethylene groups. A particularlypreferred Pluronic is the Pluronic L62 wherein the hydrophobic base hasa molecular weight of 1750 and percent by weight of the moleculeconsists of the hydrophilic polyoxyethylene groups.

It has been found that at the high temperatures of application and usethe instant lubricating compositions have a tendency to foam,consequently it is preferable although not necessary to employ ananti-foam agent. Agents particularly suitable are the silicones such asdimethyl silicone and other commercially available materials. They arepreferably introduced into the oil prior to emulsification in amountsranging between 5 and 50 parts per million based on the oil. Byintroducing anti-foam agents prior to emulsification excessive foamingduring the emulsification stage is avoided.

Since these emulsion lubricating compositions often develop mold uponstanding for any appreciable length of time before use, it is preferableto prevent this by the addition of an anti-mold agent such as thymol,chlorthymol or similar compound, generally contained in alcoholicsolutions, in amounts ranging between 0.01 percent and 0.1 percent byweight based on the weight of the final composition. It is preferable toadd the thymol solution to the mixture after the introduction of thesolid lubricant into the emulsion.

The compositions of this invention are prepared by emulsifying from 3 to300 parts by weight of the polyalkylcne glycol in 375 parts by weight ofwater using from 0.2 to 125 parts by weight of one of the abovedescribed polyoxyalkylene emulsifiers. The weight of the glycol shouldnot be more than 15 times the weight of the emulsifier, and preferablythe weight of the glycol should range from about 2 to about 4 times theweight of the emulsifier. The oil is preferably emulsified with thewater by means of a homogenizer, colloid mill or similar device in orderto produce a stable emulsion. From 1 to 100 parts by weight of the solidlubricant, i.e. graphite or molybdenum disulfide, is dispersed in theemulsion of oil and water by conventional means such as a colloid mill.The antifoam agent is added to the glycol preferably beforeemulsification and the anti-mold agent is added to the finalcomposition.

The composition thus prepared is stable and may be used directly for thelubrication of hot bakery chains. If desired and for certain particularconditions of use the described emulsion may be diluted with additionalquantities of water immediately prior to use, for example, with aquantity of water ranging from 2 to 20 times the weight of the originalemulsion. It will be understood, however, that such diluted emulsions donot possess the same stability characteristics or lubricationcharacteristics as the aforementioned original emulsion.

The following example will serve to illustrate a specific embodiment ofthe invention.

Example An emulsion containing 56 pounds of polyethylene glycol having aviscosity of 62.7 Saybolt Seconds Universal at 210 F. and 300 SayboltSeconds Universal at 100 F., a flash point of 490 F. (ASTM Method D9252)and a fire point of 585 F. (ASTM Method D9252) designated by the tradename Ucon-LB-300X was emulsified in 375 pounds of water using 22 poundsof polyoxyethylene-polyoxypropylene emulsifying agent (Pluronic L62).Prior to emulsifying the glycol with the water, 10 parts by million byweight of dimethyl silicone were added to the glycol. After the emulsionof glycol and water had been produced, pounds of finely dividedmolybdenum disulfide were dispersed therein by means of a colloid millto produce the lubricant composition. Approximately 25 grams of thymoldissolved in 50 cc. of isopropyl alcohol were added to the finalcomposition as an antimold agent.

This composition was found to be completely successful in overcoming thedisadvantages outlined hereinbefore of prior art lubricants. Whenapplied on the hot surfaces of bakery oven chains, rollers and bearingsurfaces the rate of evaporation was sufficiently low so that thelubricant penetrated the remotest parts before the evaporation of thewater and oil was completed. Upon completion of the evaporation of thewater portion of the lubricant leaving a thin, durable coating ofmolybdenum disulfide was completely dispersed.

The molybdenum disulfide was deposited throughout the various parts andwhen the temperature reached approximately 490" F., the glycol wascompletely volatilized leaving a thing, durable coating of molybdenumdisulfide bonded to the bearing surfaces.

As an added advantage it was found that upon application of thislubricant composition the various parts were flushed clean of rust andother corrosive products which had developed previously during the useof inadequate lubricating compositions. It was found after successiveapplications of the lubricant of this invention that the bearingsurfaces and adjacent parts were thoroughly cleaned and freed of rustwith the result the molybdenum sulfide lubricant was bonded to the cleanbearing surfaces and provided a durable efficient lubricating film.

It was also found that the volatilization of the liquid portion of thelubricant composition was accomplished without the formation of anyobnoxious odors or smoke since there were no sulfur or similar odorproducing compounds either in the oil phase of the emulsion or in theemusifying agent. In addition the composition provided rust protectionthroughout its period of use.

For most efficient lubrication, if graphite is used as the solidlubricant, it should be as pure as possible and free of abrasive typematerials such as silica-containing materials. Either the so-called fineor coarse grades of molybdenum disulfide may be used although it ispreferable that the particle size of the molybdenum disulfide have anaverage size of approximately one-half micron in cross sectionaldiameter since this material is more easily dispersed in the lubricantcomposition and bonded to the bearing surfaces.

I claim:

1. A lubricating composition consisting essentially of from 1 to partsby weight of a solid lubricant having a plate-like molecular structureselected from the group consisting of graphite and molybdenum disulfidedispersed in an emulsion of 3 to 300 parts by weight of a polyalkyleneglycol synthetic oil selected from the group consisting of polyethyleneglycols and polypropylene glycols, said glycols having a molecularweight in the range from 100 to about 2000 and having a viscosityranging between about 70 and 500 Saybolt Seconds Universal at 100 F.,0.2 to 125 parts by weight of a polyoxyalkylene emulsifying agentconsisting of a liquid block polymer in which the polyoxypropylenehydrophobic base has a molecular weight ranging from about 1200 to about2100 with from weight percent to about 40 weight percent of the moleculeconsisting of hydrophilic polyoxyethylene groups and 375 parts by weightof water wherein the weight of the polyalkylene glycol is not more thantimes the Weight of the polyoxyalkylene emulsifier.

2. A lubricating composition consisting essentially of from 1 to 100parts by weight of molybdenum disulfide dispersed in an emulsion of 3 to300 parts by weight of a polyalkylene glycol synthetic oil selected fromthe group consisting of polyethylene glycols and polypropylene glycols,said glycols having a molecular weight in the range from 100 to about2000 and having a viscosity ranging between about 70 and 500 SayboltSeconds Universal at 100 F., 0.2 to 125 parts by weight of apolyoxyalkylene emulsifying agent consisting of a liquid block polymerin which the polyoxypropylene hydrophobic base has a molecular weightranging from about 1200 to about 2100 with from 10 weight percent toabout 40 weight percent of the molecule consisting of hydrophilicpolyoxyethylene groups and 375 parts by weight of water wherein theweight of the polyalkylene glycol is not more than 15 times the weightof the polyoxyalkylene emulsifier.

3. A lubricating composition consisting essentially of from 1 to 100parts by weight of graphite dispersed in an emulsion of 3 to 300 partsby weight of a polyalkylene glycol synthetic oil selected from the groupconsisting of polyethylene glycols and polypropylene glycols, saidglycols having a molecular weight in the range from 100 to about 2000and having a viscosity ranging between about 70 and 500 Saybolt SecondsUniversal at 100 F., 0.2 to 125 parts by weight of a polyoxyalkyleneemulsifying agent consisting of a liquid block polymer in which thepolyoxypropylene hydrophobic base has a molecular weight ranging fromabout 1200 to about 2100 with from 10 weight percent to about 40 weightpercent of the molecule consisting of hydrophilic polyoxyethylene groupsand 375 parts by weight of water wherein the weight of the polyalkyleneglycol is not more than 15 times the weight of the polyoxyalkyleneemulsifier.

4. A lubricating composition consisting essentially of from 1 to 100parts by weight of a solid lubricant having a plate-like molecularstructure selected from the group consisting of graphite and molybdenumdisulfide dispersed in an emulsion of 3 to 300 parts by weight ofpolyethylene glycol having a viscosity ranging between about 70 and 500Saybolt Seconds Universal at 100 F., 0.2 to 125 parts by weight of apolyoxyalkylene emulsifying agent consisting of a liquid block polymerin which the polyoxypropylene hydrophobic base has a molecular weightranging from about 1200 to about 2100 with from 10 weight percent toabout 40 weight percent of the molecule consisting of hydrophilicpolyoxyethylene groups and 375 parts by weight of Water wherein theweight of the polyethylene glycol is not more than 15 times the weightof the polyoxyalkylene emulsifier.

5. A lubricating composition consisting essentially of from 1 to 100parts by weight of molybdenum disulfide dispersed in an emulsion of 3 to300 parts by weight of polyethylene glycol having a viscosity rangingbetween about 70 and 500 Saybolt Seconds Universal at F., 0.2 to partsby weight of a polyoxyalkylene emulsifying agent consisting of a liquidblock polymer in which the polyoxypropylene hydrophobic base has amolecular weight ranging from about 1200 to about 2100 with from 10weight percent to about 40 weight percent of the molecule consisting ofhydrophilic polyoxyethylene groups and 375 parts by weight of waterwherein the weight of the polyethylene glycol is not more than 15 timesthe weight of the polyoxyalkylene emulsifier.

6. A lubricating composition consisting essentially of from 1 to 100parts by weight of graphite dispersed in an emulsion of 3 to 300 partsby weight of polyethylene glycol having a viscosity ranging betweenabout 70 and 500 Saybolt Seconds Universal at 100 F., 0.2 to 125 partsby weight of a polyoxyalkylene emulsifying agent consisting of a liquidblock polymer in which the polyoxypropylene hydrophobic base has amolecular weight ranging from about 1200 to about 2100 with from 10weight percent to about 40 weight percent of the molecule consisting ofhydrophilic polyoxyethylene groups and 375 parts by weight of waterwherein the weight of the polyethylene glycol is not more than 15 timesthe weight of the polyoxyalkylene emulsifier.

7. A lubricating composition consisting essentially of from 1 to 100parts by weight of a solid lubricant having a plate-like molecularstructure selected from the group consisting of graphite and molybdenumdisulfide dispersed in an emulsion of 3 to 300 parts by weight of apolyalkylene glycol synthetic oil selected from the group consisting ofpolyethylene glycols and polypropylene glycols, said glycols having amolecular weight in the range from 100 to about 2000 and having aviscosity ranging between about 70 and 500 Saybolt Seconds Universal at100 F., 0.2 to 125 parts by weight of a polyoxyalkylene emulsifyingagent consisting of a liquid block polymer in which the polyoxypropylenehydrophobic base has a molecular weight ranging from about 1200 to about2100 with from 10 weight percent to about 40 Weight percent of themolecule consisting of hydrophilic polyoxyethylene groups and 375 partsby weight of water wherein the weight of the polyethylene glycol is notmore than 15 times the weight of the polyoxyalkylene emulsifier and theemulsion contains minor amounts of anti-foam and anti-mold agents.

8. A lubricating composition consisting essentially of from 1 to 100parts by weight of molybdenum disulfide dispersed in an emulsion of 3 to300 parts by weight of polyalkylene glycol selected from the groupconsisting of polyethylene glycol and polypropylene glycol and having aviscosity of 300 Saybolt Seconds Universal at 100 F., 0.2 to 125 partsby weight of a polyoxyalkylene emulsifying agent consisting of a liquidblock polymer in which the polyoxypropylene hydrophobic base has amolecular weight of about 1750 with 20 weight percent of the moleculeconsisting of hydrophilic polyoxyethylene groups and 375 parts by weightof water wherein the weight of the polyethylene glycol is not more than15 times the weight of the polyoxyalkylene emulsifier.

References Cited in the file of this patent UNITED STATES PATENTS1,428,148 De Cew Sept. 5, 1922 FOREIGN PATENTS 716,354 Great BritainOct. 6, 1954 OTHER REFERENCES Ucon Brand Fluid and Lubricants, bookletby Carbide and Carbon Corp, N.Y., 1957, pages 3 and 16.

1. A LUBRIACATING COMPOSITION CONSISTING ESSENTIALLY OF FROM 1 TO 100PARTS BY WEIGHT OF A SOLID LUBRICANT HAVING A PLATE-LIKE MOLECULARSTRUCTURE SELECTED FROM THE GROUP CONSISTING OF GRAPHITE AND MOLYBDENUMDISULFIDE DISPERSED IN AN EMULSION OF 3 TO 300 PARTS BY WEIGHT OF APOLYALKYLENE GLYCOL SNYTHETIC OIL SELECTED FROM THE GROUP CONSISTING OFPOLYETHYLENE GLYCOLS AND POLYPROPYLENE GLYCOLS, SAID GLYCOLS HAVING AMOLECULAR WEIGHT IN THE RANGE FROM 100 TO ABOUT 2000 AND HAVING AVISCOSITY RANGING BETWEEN ABOUT 70 AND 500 SAYBOLT SECONDS UNIERSAL AT100*F., 0.2 TO 125 PARTS BY WEIGHT OF POLYOXYALKYLENE EMULSIFYING AGENTCONSISTING OF A LIQUID BLOCK POLYMER IN WHICH THE POLYOXYPROPYLENEHYDROPHOBIC BASE HAS A MOLECULAR WEIGHT RANGING FROM ABOUT 1200 TO ABOUT2100 WITH FROM 10 WEIGHT PERCENT TO ABOUT 40 WEIGHT PERCENT OF THEMOLECULE CONSISTING OF HYDROPHILIC POLYOXYETHYLENE GROUPS AND 375 PARTSBY WEIGHT OF WATER WHEREIN THE WEIGHT OF THE POLYALKYLENE GLYCOL IS NOTMORE THAN 15 TIMES THE WEIGHT OF THE POLYOXYALKYLENE EMULSIFIER.